The City Council shall have full power after notice and hearing to regulate by ordinance the rates, charges, and fares of every public utility franchise holder operating in the City. Every franchise holder who shall request an increase in rates, charges, or fares, shall have, at the hearing of the City Council called to consider such request, the burden of establishing by clear, competent, and convincing evidence, the value of its investments properly allocable to service in the City, and the amount and character of its expenses and revenues connected with the rendering of such service. No public utility franchise holder shall institute any legal action to contest any rate, charge, or fare fixed by the City Council until such franchise holder has filed a motion for rehearing with the City Council specifically setting out each ground of its complaint against the rate, charge, or fare fixed by the City Council, and until the City Council shall have acted upon such motion. Such motion shall be deemed overruled unless acted upon by the City Council within a reasonable time, not to exceed ninety (90) days from the filing of such motion for rehearing; provided, however, the City Council may by ordinance or resolution extend such time limit for acting on said motion for rehearing from ninety (90) days to one hundred eighty (180) days.